1. Field of the Invention
The present invention relates to hearing aid systems. The invention more specifically relates to binaural hearing aid systems, configured to provide binaural beats. The invention also relates to a method of providing binaural beats.
In the context of the present disclosure, a hearing aid should be understood as a small, microelectronic device designed to be worn behind or in a human ear of a hearing-impaired user. A hearing aid system may be monaural and comprise only one hearing aid or be binaural and comprise two hearing aids. Prior to use, the hearing aid is adjusted by a hearing aid fitter according to a prescription. The prescription is based on a hearing test, resulting in a so-called audiogram, of the performance of the hearing-impaired user's unaided hearing. The prescription is developed to reach a setting where the hearing aid will alleviate a hearing loss by amplifying sound at frequencies in those parts of the audible frequency range where the user suffers a hearing deficit. A hearing aid comprises one or more microphones, a microelectronic circuit comprising a signal processor, and an acoustic output transducer. The signal processor is preferably a digital signal processor. The hearing aid is enclosed in a casing suitable for fitting behind or in a human ear.
As the name suggests, Behind-The-Ear (BTE) hearing aids are worn behind the ear. To be more precise an electronics unit comprising a housing containing the major electronics parts thereof, is worn behind the ear. An earpiece for emitting sound to the hearing aid user is worn in the ear, e.g. in the concha or the ear canal. In a traditional BTE hearing aid, a sound tube is used because the output transducer, which in hearing aid terminology is normally referred to as the receiver, is located in the housing of the electronics unit. In some modern types of hearing aids a conducting member comprising electrical conductors is used, because the receiver is placed in the earpiece in the ear. Such hearing aids are commonly referred to as Receiver-In-The-Ear (RITE) hearing aids. In a specific type of RITE hearing aids the receiver is placed inside the ear canal. This is known as Receiver-In-Canal (RIC) hearing aids.
In-The-Ear (ITE) hearing aids are designed for arrangement in the ear, normally in the funnel-shaped outer part of the ear canal. In a specific type of ITE hearing aids the hearing aid is placed substantially inside the ear canal. This type is known as Completely-In-Canal (CIC) hearing aids. This type of hearing aid requires a very compact design in order to allow it to be arranged in the ear canal, while accommodating the components necessary for operation of the hearing aid, such as microphones, a microelectronic circuit comprising a signal processor, an acoustic output transducer and a battery.
Binaural beats are auditory brainstem responses which originate in the superior olivary nucleus of each hemisphere. They result from the interaction of two different auditory impulses, originating in opposite ears and which differ in frequency between say one and 30 Hz. For example, if a pure tone of 400 Hz is presented to the right ear and a pure tone of 410 Hz is presented simultaneously to the left ear, using stereo headphones, an amplitude modulated wave of 10 Hz, the difference between the two tones, is experienced as the two wave forms mesh in and out of phase within the superior olivary nuclei. This binaural beat is not heard in the ordinary sense of the word (the human range of hearing is from 20-20,000 Hz). It is perceived as an auditory beat and can be used to entrain specific neural rhythms through the frequency-following response (FFR)—the tendency for cortical potentials to entrain to or resonate at the frequency of an external stimulus. Thus, it is possible to utilize a specific binaural-beat frequency as a consciousness management technique to entrain a specific cortical rhythm.
Binaural beats reportedly influence the brain in more subtle ways through the entrainment of brainwaves and can be used to reduce anxiety and provide other health benefits such as control over pain.
The binaural-beat appears to be associated with an electroencephalographic (EEG) frequency-following response in the brain. Many studies have demonstrated the presence of a frequency-following response to auditory stimuli, recorded at the vertex of the human brain (top of the head). This EEG activity was termed “frequency-following response” because its period corresponds to the fundamental frequency of the stimulus. The concept is that if one receives a stimulus with a frequency in the range of brain waves, the predominant brain wave frequency is said to be likely to move towards the frequency of the stimulus (a process called entrainment).
The subjective effect of listening to binaural beats may be relaxing or stimulating, depending on the frequency of the binaural-beat stimulation.
Binaural beats in the delta (1 to 4 Hz) and theta (4 to 8 Hz) ranges have been associated with relaxed, meditative, and creative states and used as an aid to falling asleep.
Binaural beats in the alpha frequencies (8 to 12 Hz) have increased alpha brain waves that have been associated with relaxation while awake, and binaural beats in the beta frequencies (typically 16 to 24 Hz) have been associated with reports of increased concentration or alertness.
When the perceived beat frequency corresponds to the delta, theta, alpha, beta, or gamma range of brainwave frequencies, the brainwaves entrain to or move towards the beat frequency.
Binaural beat stimulation has been used fairly extensively to induce a variety of states of consciousness, and there has been some work done in regards to the effects of these stimuli on relaxation, focus, attention, and states of consciousness. Studies have shown that a plastic reorganization of the brain occurs with repeated training to distinguish sounds that only exhibit minor frequency deviations.
The dominant frequency determines your current state. For example, if in someone's brain alpha waves are dominating, it is in the alpha state (this happens when one is relaxed but awake). However, also other frequencies will be present, albeit with smaller amplitudes.
2. The Prior Art
U.S. Pat. No. 6816599 B2 provides a method for synthesizing music, using a pseudo-random generator.
WO-A1-2011/006,681 provides a system for brain wave measurement. U.S. Pat. No. 8,031,892 B2 provides a hearing aid with means for shifting a signal in frequency.
It has been suggested that binaural beats can be advantageous as part of Tinnitus Retraining Theraphy (TRT). However, some experiments suggest that TRT may require about 18 months achieving observable stable effects. This kind of TRT therefore requires a considerable amount of patience and discipline from the patient.
The brain wave entraining is more effective if the entraining frequency is close to the user's starting dominant frequency. Therefore, it is suggested to start with a frequency near to one's current dominant frequency (likely to be about 20 Hz or less for a waking person), and then slowly decreasing it towards the desired frequency.
It has been suggested to induce binaural beats by providing sounds for the user that have been specially recorded and stored on some form of audio media. The sounds can be provided using headphones.
One problem with these prior art systems is that they do not encourage the user to frequent and long term training sessions, because the systems are inflexible insofar as the patient, as part of the training, can only listen to the sounds that have been specially recorded and stored on some audio media. This will typically be problematic since the user most likely will perceive it as quite boring to listen again and again to the same specially recorded sounds.
Another problem arises if the audio media is lost, damaged or for some reason not brought along by the patient.
Still another problem with the prior art is that the user's dominant brain frequency is not known at the initiation of the training, and the effectiveness of the training can therefore not be optimized by fine tuning the frequency of the induced binaural beats.
A further problem is that even if the dominant brain frequency was known it is not possible to fine tune the binaural beats in the training session to take this information into account, because the user only has to his disposal prerecorded sounds on some form of audio media.
It is therefore a feature of the present invention to provide a hearing aid system with improved means for providing binaural beats for the hearing aid user.
It is another feature of the present invention to provide an improved method for providing binaural beats.